Many types of structures include holes drilled or formed through a surface of a system component (e.g., the skin of an aircraft fuselage or wing). For example, surface holes may be used to accept rivets or other mechanical fasteners, so that a first component may be connected to a second component. In some cases, stringent requirements are specified regarding the perpendicularity of the holes, with respect to the surface of the component. For example, a requirement may specify that a hole angle (e.g., the angle of the hole sidewall, with respect to the surface) may be no more than ±2 degrees off perpendicular. When a hole is more than ±2 degrees off perpendicular, the hole may be considered to be out of tolerance.
A perpendicularity (or angularity) gage may be used to determine whether or not a hole is out of tolerance. One type of perpendicularity gage includes a digital indicator or an analog meter connected to a gage body. The gage body is adapted to accept any one of a plurality of hole probes of various diameters. To measure the perpendicularity of a hole having a particular diameter, an inspector may select a hole probe having a corresponding diameter, and may attach the selected hole probe to the gage body. The inspector may then insert the hole probe into the hole. The digital indicator may indicate the hole angle as a decimal degree reading, or alternatively, the analog meter may include a pointer, which points to the approximate hole angle along a scale. Based on the reading, the inspector may determine whether or not the hole is out of tolerance.
Although existing perpendicularity gages provide adequate functionality in many cases, they also suffer from some disadvantages. For example, when using a perpendicularity gage that includes an analog meter, the inspector may take a certain amount of time to read and interpret the pointer location on the meter to determine whether or not the hole is out of tolerance. When numerous holes are to be tested, this process may result in a lengthy inspection time. Dim ambient lighting also may affect the ability of the inspector to read the analog meter accurately and rapidly. In addition, existing perpendicularity gages may have dimensions that preclude them from being used in certain situations. For example, the analog and digital types of perpendicularity gage described above typically have gage body diameters that are substantially larger than the diameter of the hole probes. Accordingly, these perpendicularity gages can not be used to measure holes that are very close to vertical obstructions. In addition, the digital indicator adds significant height and weight to the gage, making it impractical for measuring holes located under low ceiling obstructions. Another disadvantage stems from the necessity for a hole probe for every diameter of hole to be measured. More specifically, it may be inconvenient to keep track of and change out the hole probes when measuring holes having only slight diameter variations. When a hole probe of a specific diameter is not available (e.g., it has been misplaced), the gage may be rendered unusable.
For at least these reasons, it is desirable to provide hole angularity gages which facilitate rapid out-of-tolerance decisions, which have dimensions rendering them usable in areas with close vertical or ceiling obstructions, and/or which reduce the inconvenience of having multiple hole probes. Other desirable features and characteristics of embodiments of the inventive subject matter will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.